Abstract: A pumped-fiber laser comprising a multimode doped fiber (1) and a holographic spatial mode conversion device (3).

Abstract: A pumped-fiber laser comprising a multimode doped fiber (1) and a holographic spatial mode conversion device (3).

Abstract: The device of the invention essentially comprises a plate (6) of electrooptic material, for example PLZT, on which four electrodes (7 to 10) are printed. The electric field produced by applying voltages (V1 to V4) to these electrodes creates a rotating-axis phase plate.

Abstract: The invention concerns a system for acquiring three-dimensional fingerprints, characterised in that it comprises: a medium (1) for receiving at least the object whose print is to be taken; optical image recording means (2); means for optical imaging (3) of the surface of the finger on the recording means. This system is applicable for acquiring fingerprints. It comprises various means for immobilising the hand.

Abstract: Color display system, which includes an electrooptic modulation screen (LCD) and in which a chromatic modulator (RC) is provided between the multiple-wavelength light source (S, C) and the screen (LCD). This chromatic modulator modulates a wavelength or a restricted range of wavelengths of the source in order to adjust the saturation of the various primaries transmitted to the screen as well as to effect colorimetric balance. Applications include liquid-crystal color displays.

Abstract: A holographic projection screen for large screen projection and back projection with a liquid crystal projector. The screen includes at least one layer made of a photosensitive material in which at least one index grating may be recorded by an interference of an optical recording wave with an optical object wave. The thickness of the layer is equal to or greater than n0&Lgr;2/2&pgr;, where n0 is the average index of the photosensitive material, &Lgr; is the average spacing of the index grating and &lgr; is the recording wavelength.

Abstract: A compact illumination device intended especially for illuminating an active matrix in a monochromatic or trichromatic display device. This device includes a source and collimating device in order to deliver a lighting direction from the source along a direction (Dy) and two optical components (M1) and (M2) which anamorphose the lighting in a direction parallel to the direction (Dy) and in a direction (Dz) perpendicular to the direction (Dy), respectively. These components may typically be of the holographic grating type operating in transmission or in reflection.

Abstract: Optical information recording/reading medium including at least one transparent layer (2) for recording or reading information in various strata (S1 to S3) distributed through the thickness of the medium. The medium includes, recorded in a principal plane at least the transparent layer with one or more information items (5) for carrying out either tracking, focusing, synchronization or addressing or any combination. Also included in each stratum is one more guidance information items (4).

Abstract: A display device including an illuminating source which emits radiation and a spatial light modulator illuminated by the radiation. The modulator includes a matrix of N.times.M elementary pixels (X.sub.i,j) of dimensions d.sub.N .times.d.sub.M, the pixels X.sub.i,j and X.sub.1+i,j being separated by a spacing p.sub.N. The radiation is collimated in each pixel. The spacing p.sub.N is greater by at least an order of magnitude than the dimension d.sub.M. The display may be used as a flat television screen.

Abstract: A system for the control of light beams includes a beam splitter placed on the path of the beam to be controlled and deriving a measurement beam from this beam; a detection device receiving the measurement beam and measuring the shape of the wave front of the measurement beam; a wave-front shape correction device placed on the path of the beam to be controlled, activated by the detection device and correcting the shape of the wave front of the beam to be controlled. The detection device includes a light spatial modulator providing for the selective transmission of the portions of the measurement beam; a focusing device receiving the different portions of the measurement beam; a series of photodetectors placed along the focusing plane of the focusing device; a device for the identification of the photodetector or photodetectors, detecting a light wave and computing the shape of the wave front as a function of the photodetectors identified.

Abstract: This optical filtering device includes a dichroic separator on the path of a light beam to be processed. According to the invention, it also includes a holographic filtering device situated in series with the separator on the path of the same beam. The holographic device can be oriented so as to adjust the angle of incidence of the beam and hence adjust its range of filtering wavelengths.

Abstract: The color display device includes at least a light source which emits at least two primary wavelengths and an array of holographic lenses (HL). Also included is a spatial light modulator (LCD) which includes one picture element (pixel) for each holographic lens with each pixel including one subpixel for each wavelength to be displayed. Each of the holographic lenses disperses the various wavelength and focuses each of them into one of the subpixels. The structure allows for a single lens structure for the various wavelengths.

Abstract: A UHF phase shifter including a UHF waveguide having an electrooptical element lying between two elements 3 and 4 made of materials which have permittivity higher than that of the electrooptical element. An electric polarization field is applied for controlling the electrooptical element and a UHF line is inserted into the element. The control of the orientation of the molecules of the electrooptical element allows for a variation of the index of the element as seen by the field of a UHF wave.

Abstract: This device comprises an optical source emitting a single-wavelength light beam. An index grating has been recorded in a holographic device by the interference of two plane light beams, both being beams at a single wavelength with one and the same determined value and being concurrent in the holographic device. The holographic device is illuminated by the light beam and delivers a single-wavelength beam whose radiation pattern has a limited angular passband. The wavelength of the reading beam may be different from that of the recording beams. Its orientation is then different from that of the beams.

Abstract: The invention relates to an illumination device for illuminating a display device. In a preferred embodiment, non-polarized light from a non-polarized light source is polarized by a holographic polarization beam splitting device and focused onto a liquid crystal display device by a holographic focusing device. The invention is operable with monochrome and color display devices, and allows for a high light yield independent of the useful surface area of each detector element of the display device.

Abstract: A back projection device comprises an image generator (GI), an onward reflection mirror (MR) and at least one optical component (OM) capable of reflecting certain types of light beams almost entirely and reflecting certain other types of light beams almost entirely, said component being located in the proximity of a screen (E). The selection of optical behavior of the component (OM) may be done as a function of the polarization of the light beam, or else also as a function of its orientation with respect to said component (OM). Application: displays.

Abstract: Method, system and recording medium in which the writing of information is achieved by the use of a write beam including the superposition of a first optical beam at a first wavelength and of a second beam at a second wavelength less than the first wavelength. Reading is done by the use of a second optical beam at the second wavelength. The material of the recording medium is a non-linear material exhibiting a recording threshold situated between the maximum of the sum of the energies of the two beams and an energy level situated in the vicinity of the maximum energy of the first beam.

Abstract: Disclosed is a system for the recording of data on optic disks. Presently used optic disks, which can be read with lasers working in wavelengths of the visible region (between 0.5 and 0.8 microns), have a maximum surface storage density of the order of one data bit per elementary zone having an area of about one square micrometer. Beyond this limit, the diffraction does not allow the neighboring zones to be distinguished. A means is proposed to considerably increase the storage capacities: in an elementary zone of a layer, an information bit is written not in the form of a point of absorption of a laser light but in the form of a diffraction grating with a determined pitch. Several diffraction gratings, having pitches different from one another, may be superimposed at the same position, enabling the recording, in one and the same zone, of several information bits. The diffraction gratings are made by a periodic local variation of the optic index of the layer.

Abstract: Modulation mirrors including the deformable cells (CD1 to CDn) locally modified the planarity of a reflecting surface 18. The deformable cells deform under the effect of a voltage and the control of these deformable cells is such that a control voltage V.sub.c is applied between a first and a second electrode 17, 26. A photoconductor element P1 to Pn is inserted between the second electrode 26 and the deformable cell (CD1 to CDn). A light beam (MF1 to MFn) illuminates the photoconductor element in order to obtain an elongation of the deformable cell.

Abstract: The invention relates to an illumination device in which a holographic device (HP.sub.i) separates the polarizations of an incident beam. The resulting polarized beam is transmitted to a holographic device (HL.sub.i) focusing the beam at various points of a screen. This screen may be a liquid-crystal screen (LCD).Applications: Liquid-crystal display.